He founded British consumer products company JML (John Mills Limited), and is its chairman and majority shareholder.

Mills founded Fairlane UK Ltd. which initially sold imported products at trade fairs and exhibitions, and latterly manufactured them.

Charged by Trading Standards for selling brass trinkets as gold-plated jewellery, he pleaded guilty and was fined £750.

[6] JML is a multi-channel retailer that sells consumer products through in-store video, TV shopping channels, and the internet.

[12][7] Mills contested Chipping Barnet at both general elections in February and October 1974, but was defeated both times by the Conservative former Chancellor of the Exchequer, Reginald Maudling.

[6] Mills has published a series of books on economics, exchange rate policy, the Eurozone, and manufacturing, subjects on which he also blogs.

His published books include A Critical History of Economics, Managing the World Economy, and Britain’s Achilles Heel.

[18] In September 2020, Mills published The Elephant in the Room, a book on why Britain needs to rebalance its economy after 40 years of deindustrialisation.

Mills sat on the judging panel alongside Stephanie Flanders, John Eatwell, and Helena Morrissey.

[21][22] He was married to barrister Barbara Mills, who from 1992 to 1998 was Director of Public Prosecutions, from July 1962, shortly after they both graduated from Oxford, until her death in May 2011.